1. Field of Invention
This invention relates to the field of liquid ring pumps.
2. Background Discussion
Liquid ring pumps are widely used in industrial and other applications to pump air or other gases. In a typical application, water or other liquid is introduced into the pump and centrifugally flung outwardly by a rotating rotor to form an annular ring of liquid within the stationary pump housing. The liquid ring rotates with the rotor and is centered about the longitudinal axis of the housing. The rotational axis of the rotor, however, is offset from the axis of the housing. Consequently, as the liquid ring rotates with the rotor, an air core or pocket is formed at the center of the annular liquid ring wherein the air core like the liquid ring is also centered relative to the housing axis but offset from and eccentrically positioned relative to the shaft axis.
The liquid volume in the housing is maintained to provide a seal at the outer portions of the rotor blades isolating individual chambers between adjacent blades. In one complete rotation of the rotor, liquid will first fill a chamber and then recede as the chamber advances about the housing until the chamber is almost empty of liquid wherein the chamber again fills with liquid to complete a cycle. As the liquid recedes from the chamber, it is replaced by air or other gas entering the inlet of the pump. Then, as the liquid is forced back into the rotor chamber, the air is compressed and exits through the outlet of the pump.
Two problems that presently occur in liquid ring pumps are outward leakage of fluid past the shaft seals and dynamic imbalance of the operating pump. In regard to the first problem, the liquid introduced into the liquid ring pump to form the annular ring commonly enters the pump and fills the space adjacent the shaft between the pump cone and the shaft. It then flows outwardly through passages in the cone or between the cone and the base of the rotor. The problem subsequently arises that liquid and/or gas under the pressure generated by the pump tends to leak past the shaft seal from the inboard or high pressure side of the seal to the outboard or low pressure side of the seal. Such leakage can contaminate the bearings and if the bearings are contaminated, it becomes a very expensive and time consuming ordeal to disassemble the pump and repair or repack the sealing area. Also, if the gas being pumped is combustible such as methane or gasoline fumes, exterior leakage of the fumes past the seal area can result in a potentially dangerous explosion.
Attempts to control outboard leakage after it has occurred and fluid has passed through the sealing area are known as in U.S. Pat. Nos. 4,273,343 to Visser; 2,312,837 to Jennings; and 722,219 to Fielden. However, these prior art approaches are essentially trying to clean up and contain the problem (i.e., leakage past the sealing area) after it has occurred while the present invention attempts to prevent the problem (i.e., leakage past the seal area) before it happens. In doing so, the present invention aspirates away fluid adjacent the rotating shaft and fixed cone on the inboard or high pressure side of the seal and harmlessly draws it into the pump itself. In this manner, the sealing properties of the pump seal are enhanced and the leakage problem virtually eliminated to the extent that simple lip seals can be used if desired in applications that previously called for much more expensive and harder to maintain and install sealing arrangements.
In regard to the second problem of dynamic imbalance particularly in duplex liquid ring pumps which essentially have two mirror-image pumping chambers on either side of a central partition, several U.S. patents have addressed the problem but in rather complex terms. For example, in U.S. Pat. No. 3,209,987, Jennings addressed the problem of balancing the bending moments on the pump shaft by offsetting the inlets and outlets and housing structure of the adjacent pumping chambers by 180 degrees. In his earlier U.S. Pat. No. 1,766,751, Jennings also attempted to improve dynamic balance by facing the curved blades of each rotor section in different directions, staggering the lobes, and crossing or laterally displacing the water and fluid being pumped from one side of the rotor to the other. Similarly, Nelson in his U.S. Pat. No. 2,416,538 continues along the crossover theme of Jennings by articulating only the outer portions of each blade combined with the crossing or laterally displacing of the water and fluid being pumped from one side of the rotor as in Jennings.
In contrast, the present invention addresses and improves the dynamic operation of a duplex liquid ring pump by simply offsetting the blades in each rotor section. In doing so, the rotor blades on one side of the central partition are then staggered or out of phase from the mirror-image rotor blades on the other side of the partition in the adjacent pumping chamber.